The type of device herein contemplated has particular utility in two distinct medical situations. The first situation is the type referred to in commonly assigned U. S. Pat. Nos. 3,910,260, 4,004,577, and 4,658,830. Briefly stated, in this use the device is given to designated coronary prone patients together with autoinjectors containing an antiarrythmia agent (Lidocaine) and/or a thrombolytic agent (t-PA). When the patient begins to experience symptoms of a heart attack, the patient immediately goes to the phone, calls a pre-existing central source having the patient's full medical history and standing orders of the patient's doctor. The patient then connects the electrodes of the device to his skin, e.g. armpits (see U. S. Pat. No. 3,792,700) and transmits the EKG thus acquired to the central source. The experts at the central source are then immediately able to advise the patient by virtue of the EKG information conveyed and the oral descriptions of the patient provided over the phone by the patient. Under some circumstances the advice may be for the patient to self-administer the medicament by simply operating the autoinjector. The use herein contemplated is under emergency conditions where time is of the essence.
The other use of the device is as a diagnostic adjuvant. For example, where a patient is suffering heart palpitations or other unusual events, it is desirable in diagnosing the problem to have an EKG record of the event as it is taking place. While time is of the essence in capturing the event, generally speaking an emergency situation does not prevail. Devices which have been developed for this specific use have included the capability of storing acquired electrical activity of the event for immediate play back.
As indicated it is desirable to obtain as much EKG information as can be conveniently acquired to allow a qualified medical professional to diagnose exactly what problem is occurring in the user. To do this, it is desirable to obtain many views of the heart of the user. There are many standard views of the heart which will now be explained with reference to FIG. 1.
FIG. 1 shows a stick figure diagram of a user 1 and his heart 2. A first electrode RA is shown on right arm 3 of the user. A second electrode LA is shown on left arm 4 of the user. In correspondence with the standard convention, a third electrode LL is shown on the left leg 6 of the user. A plurality of views of the heart can be obtained from these three electrodes. A first view I is established between the right arm electrode RA and left arm electrode LA. A second view II is established between the right electrode RA and the left leg electrode LL. A third view III is established between the left arm electrode and the left leg electrode. This yields three standard views of the heart. In addition, other aspects of the electrocardiograph can be obtained by center tapping between two of the electrodes and using this as an reference for the other electrode. This gives three more "augmented" views. Other views are possible by using a wye configuration, and by further electrodes V1-V6 on the chest, and by other techniques which are known in the art. It is desirable for a skilled medical practitioner to have a plurality of such views of the heart during an episode, so that he may more accurately determine the occurrences during this episode.
In accordance with the present invention, it is an object thereof to provide a portable unit which can easily be carried by the user anywhere that the user goes. This portable unit desirably should provide at least two views of the heart and preferably three to provide a skilled practitioner with sufficient information about the episode.
Moreover, when a user first begins the episode, it is desirable to obtain the information immediately. The portable unit of the present invention is adapted to play this information over a telephone line, to enable medical personnel who are standing by to immediately diagnose the problem. In emergency operations, the current heart activity is played over the telephone. However, if the user must find and get to a telephone before he can play back the heart electrical activity, the episode may be over and the medical personnel would be without sufficient information upon which to make a diagnosis. Therefore, according the present invention, information is stored in the memory means upon an initiation by the user. Therefore, when the user feels an episode beginning, the user can initiate the memory means to begin storing. Upon reaching a telephone, the user can play back the information from the memory device to the practitioners.
This has posed another problem in the prior art. Assuming that a device were known to play back multiple views of the heart, the prior art would play back these multiple views one after the other. This provides the practitioner with the desired information, but makes it very difficult for the practitioner to synchronize this information. Moreover, this lengthens the time necessary to make the diagnosis by the number of channels that will be received. In fact, if the two channels are sequentially received, the practitioner receiving both items of information would have to manually synchronize them, holding them together with tape or the like. This makes for difficult synchronization. Accordingly, the present invention includes a feature such that the multiple channels of information which are stored in the memory are simultaneously transmitted over the telephone lines. This produces a presynchronized print-out at the practitioner's end, simplifying the diagnosis for the practitioner.
The present invention also operates in a "rolling mode" where the memory is continuously storing information indicative of the electrical activity of the heart. This enables crucial information to be unambiguously stored. By the time a user feels an episode onset, the episode has already begun. The user would miss the beginning portion of this episode if he were merely to initiate the recording sequence when he felt the onset of the episode. To solve this problem, the present invention uses a rolling mode of recording. This recording mode continuously records electrical activity of the heart. New electrical activity is recorded to displace old electrical activity, therefore continuously rolling through the memory from beginning to end. Upon feeling the onset of an episode, the user can initiate the rolling recording initiation. This causes the memory to retain a certain amount of information before the initiation (e.g. 30 seconds) and to record a certain amount of information after the initiation. When the user then plays this information back over the telephone, the information includes some time before the initiation and the crucial part of the information.
Such a rolling mode has, however, been known in the art. For instance, U.S. Pat. No. 4,622,979 describes a user worn apparatus which records in a mode very similar to rolling mode. However, a problem exists in the use of this device. Specifically, the rolling mode continuously records information, and therefore the memory is always full with this information. When a user goes to play back the information, however, it is crucial that the information which is played back is the information which has most recently been recorded. Since the memory is always full, the user may be playing back information indicative of a previous episode. The present invention obviates this disadvantage by including a erase-after-record mode. This mode allows the information to be played back and then elapses a certain amount of time. An elapse of this certain amount of time is necessary to ensure that the receiving end has received the information properly, and that another playback will not be necessary. After this time is elapsed, this mode automatically erases the contents of the memory. Therefore, it becomes impossible for user to later play this back while erroneously thinking it is the current information.
Heart patients also typically do not want to cause a commotion by having others around them thinking that they are beginning to undergo a heart attack. However, previous portable information devices have made an audio sound while they record the heart attack information. If a user thinks he is going to cause a commotion by recording the onset of an episode, this user will have a more difficult choice to make. Should he begin recording the episode and cause himself possible embarrassment, or is this really an episode at all? Users should never be faced with such choice, as they should always be recording every episode which could possibly occur. Therefore, the present invention also includes another advantageous mode wherein a single episode can be recorded with speaker-off. In this way, the user will be spared any possible embarrassment. This leads the user to more likely record the information.
Devices which are superficially similar to the present invention are also known to the inventors of the present invention. One such item is the retrospective (TM) ECG memory loop recorder marketed by Cardiac Evaluation Center Incorporated, Milwaukee, Wis. 53222. This device reads a plurality of channels of information and also operates in a similar rolling mode. This device also recognizes the problem of sending old data erroneously, when intending to send current data but merely relies on some manual tone played to the user to ensure against it. There is absolutely no way to automatically cause the retrospective device to automatically erase. This device uses a dual channel mode and recognizes that this enhances diagnosis. However, in order to maintain this device compatible with single channel receivers, it transmits 30 seconds of channel 1 and then 30 seconds of channel 2. This has disadvantages discussed above, in that the practitioner must somehow evaluate this information. The Memorytrace (TM) unit by Cardiocare also has dual channel recording capability. This device also operates in a equivalent to the rolling mode. However, this device also does not include the advantageous features discussed above.
U.S. Pat. No. 4,550,370 also relates to a similar system.
U.S. Pat. No. 4,679,144 relates to a system which obtains information for real time analysis of EKG information. This information is A to D converted and stored in a RAM for later read out. However, the advantages of the present invention are not obtained.
Similar devices are also described in U.S. Pat. Nos. 4,535,783; 4,592,018; 4,164,215; 4,593,702; and 3,132,643. However, none of these patents teach advantageous features of the present invention. A particularly preferred embodiment of this invention uses underarm or armpit electrodes such as the type described in U.S. Pat. No. 3,938,507, the disclosure of which is hereby incorporated by reference. In combination with these two armpit electrodes, the most preferred embodiment of the present invention uses a third electrode to operate as the LL electrode. This third electrode is adapted to be inserted into the belt of a user to provide multiple views of the heart.
A two electrode system is also described in our co-pending application "MONITORING DEVICE WITH DUAL POSITION ELECTRODES", inventors H.E. Reinhold and D.J. Greenwold, filed Mar. 25, 1988, Ser. No. 07/172,840, the disclosure of which is expressly incorporated herein by reference.
Specifically, the present invention relates to a portable measuring device for measuring the electronic activity of the heart of the user. This device includes a connector for receiving signals indicative of at least two electrical leads o activity of the heart of the user. These signals are amplified to produce at least first and second electrical activity signals. These electrical activity signals, as amplified, are then stored in a memory. An audio information producing structure is provided that produces audio signals of a form suitable for transmission over the telephone lines. A control device controls the operation of this whole apparatus. A first mode of the control device allows the device to operate in a live mode by connecting signals from the input of the memory to the audio information producing device. Thereafter, the signals which are obtained on the connector are connected directly to the audio information producing device. A second mode commands the memory to record in the rolling mode in which information is continuously being stored in the memory, new information erasing previous information. A third mode commands the memory to store information for a time interval. This third mode can be operated with the audio information producing structure either on (producing audio information) or off (silent). A playback mode includes at least a simultaneous mode in which information from the two channels is simultaneously played back over the telephone line.
According to another aspect of the invention, this operation can also follow a sequential mode where the first channel played back is followed by a second channel being played back.
Yet another aspect of the invention erases the contents of the memory some predetermined time after sending. The memory means is preferably a digital memory, so that an A to D converter and D to A converter may be used to interface with this memory means. The amplifying means is preferably a differential amplifier while the audio information producing means includes a voltage controlled oscillator operating at 1700 hertz and an audio amplifier and speaker.